I thought about the spelling a word but I wasn't sure what to use. Since I teach 6th grade, I didn't know what word would be best.
The other 3 sixth grade teachers use DOJO but I am just not that "techy". Maybe I should learn!!

It works on the same premise as those cards you get from businesses, like coffee places. The business initials or punches your card each time you purchase, say, a coffee, and when you get all punched, you get a free coffee. I've attached my copy.

For my cards, kids need to earn 20 punches before filing up the card. They may use the card for a free homework assignment, free spelling test, or anything you want it to count for.

Depending on the age/grade of the students, you might want to institute some kind of class or team point system. I've done it both ways, having individual teams get points or having classes get points.

You can offer rewards for reaching in specific goals such as 10, 20, 30, 40, 50, etc. I'm currently doing that with only moderate success this year (last year the kids were super competitive and worked hard to keep each other in line so that they could earn points). The rewards that I give, and the class has to vote on whether or not to use the points, are things like being able to choose their seat for the day, getting popcorn during class, a homework pass for the entire class, the teacher bringing in donuts, or getting a video for the class period. Obviously you can tailor the rewards to fit the interests of your students.

You could implement a marble reward system, filling a jar with one marble whenever the class provides you with the desired behavior. After a certain amount of marbles in the jar, depending on what you want, the class can spin a wheel that has rewards (free homework day, lunch with the teacher, etc.). The students will want to fill the jar as fast as possible. You can also morph this and have a jar for each student and do the same technique!